The present invention relates to an image forming device and a cartridge unit capable of preventing different colored inks from mixing when exchanging a cartridge unit filled with one colored ink with that filled with another colored ink and capable of reducing load imparted on a driving means for driving a print head.
There has been known an ink jet type print device having a print head. Ink is supplied to the print head from an ink-filled ink cartridge. The print head ejects the ink onto a print sheet in order to print characters and the like. A variety of configurations are known for supplying ink from a cartridge to a print head. For example, Japanese Patent Application Publication (Kokai) HEI-5-218 discloses an ink cartridge connected by an ink supply tube to a print head, which is mounted on a carriage of a printing device. Ink filling the ink cartridge is supplied through the ink supply tube to the print head.
However, with this configuration, when the ink cartridge in this printing device is to be exchanged for a new one, ink from the old ink cartridge can remain in the ink supply tube and in the print head when the new cartridge is exchanged. When an ink cartridge filled with one color of ink is replaced with an ink cartridge filled with a different color of ink, then the ink remaining in the ink supply tube and the print head can undesirably mix with the ink in the new ink cartridge. For example, if the ink cartridge presently mounted on the carriage is filled with black ink and the ink cartridge to replace the present ink cartridge is filled with magenta colored ink, then the black ink remaining in the ink supply tube and the print head can mix into the newly supplied magenta colored ink and change the color of the magenta colored ink.
Japanese Patent Publication (Kokoku) SHO-62-42792 discloses a print head cartridge configured from an integral print head and ink tank. A printing device using this print head cartridge can print in a desired color when a print head cartridge filled with a desired colored ink is mounted onto the carriage of the printing device. Further, when the print head cartridge is exchanged, the print head is also exchanged, so undesirable mixing of different colored inks can be prevented.
Since the print head cartridge includes not only the print head but also the ink tank, the load weight on the carriage includes not only the print head but also the ink tank. Therefore, the carriage motor for driving the carriage must be large enough to also move the weight of the ink tank, thereby requiring a large carriage motor. Further, a large amount of power is used for driving the carriage motor.
Further, as the ink stored in the ink tank is consumed during printing operations, the load on the carriage drops. As a result, the load imparted on the carriage motor fluctuates over time. When the load on the carriage motor fluctuates, the moving speed of the carriage also fluctuates so that it is difficult to obtain uniform and proper printing quality. As a result, there is a need to provide a separate control means for controlling moving speed of the carriage in association with change in the amount of ink in the ink tank. This special control device increases the production costs of the printing device.
Japanese Patent Application Publication (Kokai) HEI-6-234209 discloses a printing device having a print head and an ink tank connected together by an ink supply tube. The print head and ink tank form a unit that can be exchanged by detaching the unit from the main body of the printing device. The ink tank is fixed to a predetermined position of the unit, and only the print head is mounted on the carriage of the printing device.
Therefore, even when the ink in the ink tank is consumed during printing operations, load on the carriage will remain the same. For this reason, load on the carriage motor will also remain stable so that uniform and proper printing quality can be achieved. Further, printing can be performed in the desired colored ink by mounting a unit, including an ink tank filled with a desired colored ink, onto the main body of the printing device. By exchanging the unit, the print head is also exchanged so that undesirable mixing of different colored inks can be prevented.